Filter and air-conditioning device

ABSTRACT

A filter that includes a plurality of fibers arranged to form a first principal surface and a second principal surface opposite the first principal surface, and a plurality of first piezoelectric fibers that generate negative charges by stretching are arranged at least on a side of the first principal surface.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International applicationNo. PCT/JP2018/035924, filed Sep. 27, 2018, which claims priority toJapanese Patent Application No. 2017-201241, filed Oct. 17, 2017, andJapanese Patent Application No. 2018-062193, filed Mar. 28, 2018, theentire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

One embodiment of the present invention relates to a filter and anair-conditioning device.

BACKGROUND OF THE INVENTION

Conventionally, many proposals have been made on antibacterial filters(see Patent Document 1). The mask filter disclosed in Patent Document 1is made by applying a viscous agent to a meshed fabric having meshopenings which open through the thickness, adding adhesive force to themeshed fabric, and attracting activated charcoal particles to the meshedfabric to which the adhesive force is added.

Patent Document 1: Japanese Patent Application Laid-Open No. 2006-320491

SUMMARY OF THE INVENTION

The mask filter disclosed in Patent Document 1 still needs to beimproved in terms of removal of fine particles such as dust or bacteria.

Therefore, an object of one embodiment of the present invention is toprovide a filter and an air-conditioning device capable of effectivelyremoving fine particles.

The filter according to one embodiment of the present invention includesa plurality of fibers arranged to form a first principal surface and asecond principal surface opposite to the first principal surface, and,of the plurality of fibers, a plurality of first piezoelectric fibersthat generate negative charges by stretching are arranged at least on aside of the first principal surface.

The filter according to one embodiment of the present inventiongenerates a negative charge on the side of the first principal surfacewhen stretched in use. In general, germs and fungi are negativelycharged. Therefore, the filter can rebound germs and fungi coming closeto the side of the first principal surface. In addition, the filter canattract and capture positively charged fine particles. Thus, it ispossible to prevent the germs and fungi from entering into the filter.The piezoelectric fibers according to one embodiment of the presentinvention may include at least one of a plurality of first piezoelectricfibers that generate negative charges and a plurality of secondpiezoelectric fibers that generate positive charges.

Conventionally, there has been known that an electric field can inhibitthe growth of germs and fungi (see, for example, “BiseibutsuSeigyo—Kagaku to Kougaku” (microbiological control—science andengineering) authored by Testuaki TSUCHIDO, Hiroki KOURAI, HideakiMATSUOKA, and Junichi KOIZUMI, published by Kodansha Scientific. Seealso, for example, “Agricultural and Food Processing Applications ofHigh-Voltage and Plasma Technologies” written by Koichi TAKAKI, J. HTSJ,Vol. 51, No. 216). A potential which produces the electric field maycause an electric current to flow in a current path formed due tohumidity or the like, or in a circuit formed through a local phenomenonof microdischarge. It is considered that the electric current may weakenbacteria themselves and inhibit the growth of bacteria. The filteraccording to one embodiment of the present invention may include aplurality of first piezoelectric fibers that generate negative chargesby stretching, so that an electric field is produced between the fibers,or when it comes close to an object having a given potential (includinga ground potential) of a human body or the like. Alternatively, theplurality of first piezoelectric fibers allow an electric current toflow through moisture such as sweat between the fibers, or when theycome close to an object having a given potential (including a groundpotential) of a human body or the like.

Accordingly, in the filter according to one embodiment of the presentinvention, the plurality of first piezoelectric fibers exhibit anantibacterial effect by the following reasons. Therefore, cell membranesof bacteria or an electron transfer system for maintaining bacteria lifeare damaged to thereby kill bacteria or weaken bacteria themselves, dueto a direct action of the electric field or current that is producedwhen applied to an object (clothes, footwear, or medical articles suchas a mask) used by being brought close to an object having a givenpotential, such as a human body. Further, the electric field or currentmay convert oxygen contained in moisture into active oxygen species, orstress environment caused by the presence of the electric field orcurrent may produce oxygen radicals in cells of bacteria. The action ofthe active oxygen species including these radicals can kill or weakenbacteria. In addition, an antibacterial effect may be produced incombination of the above reasons. The term “antibacterial” used in thepresent invention may include both an effect of inhibiting thegeneration of bacteria and an effect of killing bacteria.

Further, since a piezoelectric body is used, an electric field isproduced by a piezoelectric effect, so that no power supply is required,and an electric shock may not occur. The life of the piezoelectric bodylasts longer than the antibacterial effect of chemicals or the like.Further, the piezoelectric body may cause an allergic reaction less thanchemicals.

The filter according to a second embodiment of the present inventionincludes a plurality of fibers arranged to form a first principalsurface and a second principal surface opposite to the first principalsurface, and, of the plurality of fibers, a plurality of secondpiezoelectric fibers that generate positive charges by stretching arearranged at least on the side of the second principal surface.

The filter according to second embodiment of the present inventiongenerates a positive charge on the side of the second principal surfacewhen stretched in use. Therefore, the filter can attract germs and fungicoming close to the side of the second principal surface. In addition,the filter can rebound positively charged fine particles. Thus, it ispossible to prevent the germs and fungi from entering into the filter.

The air-conditioning device according to an embodiment of the presentinvention includes the filter, an inlet port, an exhaust port, and acommunicating passage that communicates between the inlet port and theexhaust port, in which the filter is arranged in the communicatingpassage.

Since the air-conditioning device according to an embodiment of thepresent invention includes the filter, it can attract fine particlessuch as pollen or yellow dust.

According to the present invention, a filter and an air-conditioningdevice capable of effectively removing fine particles can be achieved.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1(A) is a view showing a configuration of a first piezoelectricfiber, FIG. 1(B) is a cross-sectional view taken along the line A-A inFIG. 1(A), FIG. 1(C) is a view showing a configuration of a secondpiezoelectric fiber, and FIG. 1(D) is a cross-sectional view taken alongthe line B-B in FIG. 1(C).

FIG. 2(A) and FIG. 2(B) are views showing a relationship of a uniaxiallystretching direction of polylactic acid, an electric field direction,and deformation of a piezoelectric yarn.

FIG. 3(A) illustrates shear stress generated in the piezoelectric fiberswhen a tension is applied to the first piezoelectric fibers, and FIG.3(B) illustrates shear stress generated in the piezoelectric fibers whena tension is applied to the second piezoelectric fibers.

FIG. 4(A) is a view showing potentials in the first piezoelectric fiberand the second piezoelectric fiber, and FIG. 4(B) is a view showing anelectric field.

FIG. 5(A) is a schematic view showing a configuration of anantibacterial mask according to a first embodiment, and FIG. 5(B) is aschematic view showing a configuration of an antibacterial maskaccording to a second embodiment.

FIG. 6 is a schematic view showing a configuration of an antibacterialmask according to a third embodiment.

FIG. 7(A) is a schematic view showing a configuration of anantibacterial mask according to a fourth embodiment, and FIG. 7(B) is aschematic view showing a configuration of an antibacterial maskaccording to a fifth embodiment.

FIG. 8 is a schematic view showing a configuration of an antibacterialmask according to a sixth embodiment.

FIG. 9(A) is a schematic view showing a configuration of anantibacterial gauze according to a seventh embodiment, FIG. 9(B) is aschematic view showing a configuration of an antibacterial gauzeaccording to an eighth embodiment, and FIG. 9(C) is a schematic viewshowing a configuration of an antibacterial gauze according to a ninthembodiment.

FIG. 10(A) is a schematic view of a filter according to a tenthembodiment, and FIGS. 10(B) and 10(C) are cut end views taken along theline C-C in FIG. 10(A).

FIGS. 11(A) to 11(D) are schematic views showing configurations of thefilter according to the tenth embodiment.

FIG. 12(A) is a schematic view of a modification 1 of the filteraccording to the tenth embodiment, and FIGS. 12(B) and 12(C) are cut endviews taken along the line D-D in FIG. 12(A).

FIG. 13(A) is a schematic view of a modification 2 of the filteraccording to the tenth embodiment, and FIGS. 13(B) and 13(C) are cut endviews taken along the line E-E in FIG. 13(A).

FIG. 14(A) is a schematic view of a modification 3 of the filteraccording to the tenth embodiment, and FIGS. 14(B) and 14(C) are cut endviews taken along the line F-F in FIG. 14(A).

FIG. 15 is a schematic view showing a case where a filter is used in anair-conditioning device.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1(A) is a view showing a configuration of a first piezoelectricfiber, FIG. 1(B) is a cross-sectional view taken along the line A-A inFIG. 1(A), FIG. 1(C) is a view showing a configuration of a secondpiezoelectric fiber, and FIG. 1(D) is a cross-sectional view taken alongthe line B-B in FIG. 1 (C). FIGS. 1(A) to 1(D) show a piezoelectricfiber obtained by twisting seven piezoelectric yarns 100 as an example.The number of piezoelectric yarns 100, however, is not limited thereto,and, in practice, it is properly set considering the uses of the yarn.The piezoelectric fiber is not limited to a fiber obtained by twisting aplurality of piezoelectric yarns, and may be a covered yarn obtained bywinding a piezoelectric film around a space for a core yarn or an axialcore. Further, for convenience of description, piezoelectric fibers thatform a filter and piezoelectric yarns that form a piezoelectric fiberwill be described first, and the filter will then be described.

The piezoelectric yarn 100 is an example of the piezoelectric fiber(electric charge generating yarn) that generates an electric charge bystretching. The piezoelectric yarn 100 is made of a functional polymer,for example, a piezoelectric polymer. Examples of the piezoelectricpolymer include polylactic acid (PLA). Polylactic acid (PLA) is apiezoelectric polymer not having pyroelectricity. Polylactic acid isuniaxially stretched to have piezoelectric properties. Polylactic acidincludes PLLA in which an L-form monomer is polymerized, and PDLA inwhich a D-form monomer is polymerized. The piezoelectric yarn 100 mayfurther include polymers other than the functional polymer as long as itdoes not impair the function of the functional polymer.

Polylactic acid is a chiral polymer and has a spiral structure in itsmain chain. The polylactic acid exhibits piezoelectric properties whenmolecules are oriented by uniaxially stretching. Further, when heattreatment is applied to the polylactic acid to enhance itscrystallinity, the polylactic acid has an increased piezoelectricconstant. The piezoelectric yarn 100 made of uniaxially stretchedpolylactic acid has d₁₄ and d₂₅ tensor components as piezoelectricstrain constants when the thickness direction of the piezoelectric yarn100 is defined as a first axis, a stretching direction 900 thereof isdefined as a third axis, and a direction perpendicular to both the firstand third axes is defined as a second axis. Accordingly, polylactic acidmost efficiently generates an electric charge when a strain occurs in adirection at an angle of 45° to the uniaxially stretching direction.

FIG. 2(A) and FIG. 2(B) are views showing a relationship of a uniaxiallystretching direction of polylactic acid, an electric field direction,and deformation of the piezoelectric yarn 100. As shown in FIG. 2(A),when the piezoelectric yarn 100 shrinks in a direction of a firstdiagonal line 910A and stretches in a direction of a second diagonalline 910B perpendicular to the first diagonal line 910A, an electricfield is produced in a direction from the back plane to the front planeof the paper. That is, the piezoelectric yarn 100 generates a negativecharge on the front side of the paper plane. As shown in FIG. 2(B), evenwhen the piezoelectric yarn 100 stretches in the first diagonal line910A and shrinks in the second diagonal line 910B, an electric charge isgenerated, but the polarity is reversed, and an electric field isproduced in a direction from the front plane to the back plane of thepaper. That is, the piezoelectric yarn 100 generates a positive chargeon the front side of the paper plane.

Since polylactic acid generates the piezoelectric properties due tomolecular orientation processing by stretching, it does not need to besubjected to polling processing as other piezoelectric polymers such asPVDF or piezoelectric ceramic. The uniaxially-stretched polylactic acidhas a piezoelectric constant of approximately 5 to 30 pC/N, which is anextremely high piezoelectric constant among polymers. Further, thepiezoelectric constant of the polylactic acid does not vary with timeand is extremely stable.

The piezoelectric yarn 100 is a fiber having a circular cross section.The piezoelectric yarn 100 is manufactured, for example, by a method ofextruding a piezoelectric polymer to form a fiber; a method ofmelt-spinning a piezoelectric polymer to form a fiber (including, forexample, a spinning and stretching method of separately performing aspinning step and a stretching step; a direct stretching methodperformed in combination with a spinning step and a stretching step; aPOY-DTY method capable of simultaneously performing a false-twistingstep; or an ultra high-speed prevention method to increase speed; andthe like); a method of dry-spinning or wet-spinning a piezoelectricpolymer (including, for example, a phase separation method or a dry-wetspinning method for forming a fiber by melting a polymer as a rawmaterial in a solvent and extruding the polymer from a nozzle; agel-spinning method for forming a fiber by uniformly rendering thepolymer into gel form with a solvent contained; a liquid crystalspinning method for forming a fiber by using a liquid crystal solutionor a melted body; and the like) to form a fiber; a method ofelectrostatic spinning a piezoelectric polymer to form a fiber; or thelike. The cross sectional shape of the piezoelectric yarn 100 is notlimited to a circle.

A first piezoelectric fiber 31 and a second piezoelectric fiber 32 formsuch a yarn (multifilament yarn) obtained by twisting a plurality ofPLLA piezoelectric yarns 100. The first piezoelectric fiber 31 is aright-twisted yarn (hereinafter referred to as an S yarn) obtained bytwisting the piezoelectric yarn 100 to the right. The secondpiezoelectric fiber 32 is a left-twisted yarn (hereinafter referred toas a Z yarn) obtained by twisting the piezoelectric yarn 100 to theleft.

The stretching directions 900 of the respective piezoelectric yarns 100are in line with the axial directions of the piezoelectric yarns 100. Inthe first piezoelectric fiber 31, the stretching direction 900 of thepiezoelectric yarn 100 is angled leftward with respect to the axialdirection of the first piezoelectric fiber 31. In the secondpiezoelectric fiber 32, the stretching direction 900 of thepiezoelectric yarn 100 is angled rightward with respect to the axialdirection of the second piezoelectric fiber 32. The inclination angle ofthe stretching direction 900 with respect to the axial direction of thefirst piezoelectric fiber 31 or the second piezoelectric fiber 32depends on the number of twists of the first piezoelectric fiber 31 orthe second piezoelectric fiber 32. Therefore, the first piezoelectricfiber 31 and the second piezoelectric fiber 32 can adjust theinclination angles of the piezoelectric yarns 100 with respect to theaxial directions of the first piezoelectric fiber 31 and the secondpiezoelectric fiber 32 by adjusting the number of twists thereof.

FIG. 3(A) illustrates shear stress generated in the piezoelectric fiberswhen a tension is applied to the first piezoelectric fibers, and FIG.3(B) illustrates shear stress generated in the piezoelectric fibers whena tension is applied to the second piezoelectric fibers.

As shown in FIG. 3(A), in the case where a tension is applied to thefirst piezoelectric fiber 31 of the S yarn, the surface of the firstpiezoelectric fiber 31 becomes such a state as shown in FIG. 2(A). Thisgenerates a negative charge on the surface of the first piezoelectricfiber 31 and a positive charge inside thereof. On the other hand, asshown in FIG. 3(B), in the case where a tension is applied to the secondpiezoelectric fiber 32 of the Z yarn, the surface of the secondpiezoelectric fiber 32 becomes such a state as shown in FIG. 2(B). Thisgenerates a positive charge on the surface of the second piezoelectricfiber 32 and a negative charge inside thereof.

Each of the first piezoelectric fiber 31 and the second piezoelectricfiber 32 produces an electric field due to the potential differencegenerated by these electric charges. The electric field leaks toadjacent spaces to form an electric field associated with otherportions. When the potential produced in the first piezoelectric fiber31 or the second piezoelectric fiber 32 comes close to an object havinga given potential adjacent thereto, for example, a given potential(including a ground potential) of a human body or the like, an electricfield is produced between the first piezoelectric fiber 31 or the secondpiezoelectric fiber 32 and the object.

Conventionally, there has been known that an electric field can inhibitthe growth of germs and fungi (see, for example, “BiseibutsuSeigyo—Kagaku to Kougaku” (microbiological control—science andengineering) authored by Testuaki TSUCHIDO, Hiroki KOURAI, HideakiMATSUOKA, and Junichi KOIZUMI, published by Kodansha Scientific. Seealso, for example, “Agricultural and Food Processing Applications ofHigh-Voltage and Plasma Technologies” written by Koichi TAKAKI, J. HTSJ,Vol. 51, No. 216). A potential which produces the electric field maycause an electric current to flow in a current path formed due tohumidity or the like, or in a circuit formed through a local phenomenonof microdischarge. It is considered that the electric current may weakenbacteria themselves and inhibit the growth of bacteria. The bacteria asused in this embodiment include germs, fungi, or microorganism such asmites or fleas.

Therefore, the first piezoelectric fiber 31 directly exerts anantibacterial effect due to the electric field formed near the firstpiezoelectric fiber 31 or the electric field generated when the firstpiezoelectric fiber 31 comes close to an object having a given potentialof a human body or the like. Alternatively, the first piezoelectricfiber 31 allows an electric current to flow through moisture such assweat, when it comes close to an object having a given potential ofanother adjacent fiber, a human body, or the like. The firstpiezoelectric fiber 31 may also directly exert an antibacterial effectdue to such an electric current. Alternatively, the first piezoelectricfiber 31 may indirectly exert an antibacterial effect due to activeoxygen species which oxygen contained in moisture is converted into bythe action of an electric current or a voltage, radical speciesgenerated by the interaction with an additive contained in the fibers orcatalysis, or other antibacterial species (amine derivatives or thelike). Alternatively, stress environment caused by the presence of theelectric field or current may produce oxygen radicals in cells ofbacteria. This may allow the first piezoelectric fiber 31 to indirectlyexert an antibacterial effect. In addition, the second piezoelectricfiber 32 can also directly or indirectly exert an antibacterial effectin the same manner as the first piezoelectric fiber 31. As the radical,superoxide anion radical (active oxygen) or hydroxyl radical may begenerated. The term “antibacterial” used in this embodiment may includeboth an effect of inhibiting the generation of bacteria and an effect ofkilling bacteria.

FIG. 4(A) is a view showing potentials in the first piezoelectric fiberand the second piezoelectric fiber, and FIG. 4(B) is a view showing anelectric field. FIGS. 4(A) and 4(B) show a piezoelectric fiber obtainedby twisting seven piezoelectric yarns as an example.

In the case where the first piezoelectric fiber 31 (S yarn) and thesecond piezoelectric fiber 32 (Z yarn) are formed of PLLA, the surfaceof the first piezoelectric fiber 31 alone becomes negative and theinside thereof becomes positive when a tension is applied thereto. Thesurface of the second piezoelectric fiber 32 alone becomes positive andthe inside thereof becomes negative when a tension is applied thereto.

Here, when the first piezoelectric fiber 31 of the S yarn and the secondpiezoelectric fiber 32 of the Z yarn are brought close to each other, arelatively strong electric field can be produced between the firstpiezoelectric fiber 31 and the second piezoelectric fiber 32. Forexample, the center portion of the Z yarn has a negative potential andthe center portion of the S yarn has a positive potential so that theclose portions (surfaces) have the same potential. In this case, theportion where the first piezoelectric fiber 31 and the secondpiezoelectric fiber 32 are close to each other has 0 V, and the positivepotential at the inside of the first piezoelectric fiber 31 is furtherincreased so as to keep the original potential difference. Similarly,the negative potential at the inside of the second piezoelectric fiber32 is further lowered.

The cross section of the first piezoelectric fiber 31 primarily forms anelectric field outward from the center and the cross section of thesecond piezoelectric fiber 32 primarily forms an electric field inwardfrom the center. In the case where the first piezoelectric fiber 31 andthe second piezoelectric fiber 32 are brought close to each other, theseelectric fields leak into the air to form an associated electric field,and an electric field circuit is formed between the first piezoelectricfiber 31 and the second piezoelectric fiber 32. That is, the potentialdifference at each point is defined by an electric field couplingcircuit formed by complicatedly intertwining fibers, or a circuit formedby a current path which is accidentally formed in the yarn due tomoisture or the like.

FIG. 5(A) is a schematic view showing a configuration of anantibacterial mask according to a first embodiment, and FIG. 5(B) is aschematic view showing a configuration of an antibacterial maskaccording to a second embodiment.

As shown in FIG. 5(A), an antibacterial mask 51 according to the firstembodiment includes a filter 101. The drawing shows only a filter in theantibacterial mask, and the rest are omitted. The same applies to thedescriptions of the second to sixth embodiments.

The filter 101 is formed, for example, in a rectangular shape so as tocover the mouth or nose of a human. The filter 101 includes a firstprincipal surface 21 and a second principal surface 22 which ispositioned opposite to the first principal surface 21. In theantibacterial mask 51, the second principal surface 22 is positioned onthe side of a user U. The shape of the filter 101 is not limited to therectangular shape, and may be a rhombus, a polygon, a circle, or anellipse.

The filter 101 includes an outer layer 11 and an inner layer 12. Theouter layer 11 is arranged on the side of the first principal surface21, and the inner layer 12 is arranged on the side of the secondprincipal surface 22. A plurality of first piezoelectric fibers 31 arearranged in the outer layer 11 on the side of the first principalsurface 21. For example, the outer layer 11 includes a knitted fabricmade by knitting the first piezoelectric fibers 31 as knitting yarns, anonwoven fabric including the first piezoelectric fibers 31, or a wovenfabric by weaving the first piezoelectric fibers 31.

The yarn constituting the filter 101 may include yarns other than thefirst piezoelectric fibers 31 that generate negative charges on theirsurfaces. By adjusting the amount of the first piezoelectric fibers 31,the ratio of the polarity of the electric charges to be generated can beadjusted for a particular application. In general, a piezoelectric fiberis worse in texture than cotton or the like, so that when a user wearsit, the skin may be irritated. For this reason, when the yarn (cotton,etc.) which does not generate an electric charge is partially used inthe filter 101, the texture of the filter 101 is improved, and theirritation to the skin is reduced.

Since a piezoelectric body is used in the filter 101, an electric fieldcan be produced by a piezoelectric effect. Therefore, no power supply isrequired, and an electric shock may not occur in the filter 101. Thelife of the piezoelectric body lasts longer than the antibacterialeffect of chemicals or the like. Further, the piezoelectric body maycause an allergic reaction less than chemicals.

When the filter 101 is stretched in use, negative charges are generatedon the surfaces of the first piezoelectric fibers 31 in the outer layer11. When negatively charged germs and fungi 81 come close to the side ofthe first principal surface 21, the negative charges generated by thefirst piezoelectric fibers 31 rebound such germs and fungi 81. This canprevent the germs and fungi 81 from entering into the filter 101.

The entire filter 101 may be formed of the first piezoelectric fibers31. The filter 101 may have a filter formed of the first piezoelectricfibers 31 added in a frame shape to the margin of the filter formed ofan ordinary cloth. When the filter formed of the first piezoelectricfibers 31 is provided in a frame shape, the ordinary cloth positioned atthe center thereof is likely to attract the germs and fungi 81. Thus, itis possible to prevent the germs and fungi 81 from being absorbed into abody by attracting the germs and fungi 81 that have not been reboundedby the first piezoelectric fibers 31 to the ordinary cloth.

The entire filter 101 may not be uniformly formed. For example, thefabric of the filter 101 is formed so as to have a coarse mesh at thecenter portion and a finer mesh toward the end thereof. In addition, thefilter 101 may have the first piezoelectric fibers 31 partially arrangedby combining an ordinary cloth with the first piezoelectric fibers 31 ina patchwork form.

In the case where the ordinary cloth is combined with the filter 101, anegative charge generated from the entire filter 101 becomes smaller, ascompared with the case where the entire filter 101 is formed of thefirst piezoelectric fibers 31, so that the effect of rebounding thegerms and fungi 81 becomes weak. However, the first piezoelectric fibers31 may rebound the germs and fungi 81 before the ordinary cloth attractsthem, so that a certain degree of antibacterial effect can be exerted.In addition, in the case where the ordinary cloth is combined with thefilter 101, not only the antibacterial effect but also air permeabilitycan be ensured because the ordinary cloth is excellent inhygroscopicity.

In the case where the ordinary cloth is combined with the filter 101,the ratio of the ordinary cloth to the first piezoelectric fibers 31 ispreferably 2:8 to 8:2 in terms of an area ratio. When the filter 101includes the ordinary cloth at a given ratio, it can attract the germsand fungi 81 at a certain extent and can ensure air permeability.Further, when the filter 101 includes the first piezoelectric fibers 31at a given ratio, it can sufficiently rebound the germs and fungi 81.

The shape of the antibacterial mask 51 is not limited to a general maskshape that covers a mouth or nose of a human, and may be, for example, ashape that covers only a mouth of a human. This prevents the germs andfungi 81 from entering into the mouth. Further, since the filter 101rebounds the germs and fungi 81 in the surroundings, it prevents thegerms and fungi 81 around a nose from entering into the nose. Thus, theuse of the antibacterial mask 51 having this shape allows the germs andfungi 81 to be prevented from entering into the mouth or nose, as wellas allowing the user to easily breathe because the nose is exposed tothe outside.

The first piezoelectric fibers 31 used in the filter 101 may includeyarns that generate different quantities of electric charges. In thecase where the germs and fungi 81 adhere to the filter 101, a potentialdifference is produced in the filter 101, and the potential differencethus produced can provide an antibacterial effect. The yarns thatgenerate different quantities of electric charges may be the oneobtained by combining yarns having the different number of times oftwisting, the one obtained by combining yarns having the differentnumber of times of twisting partially in a yarn, or the one obtained bycombining both of them.

An antibacterial mask according to the second embodiment will bedescribed hereinbelow. In the description of the antibacterial maskaccording to the second embodiment, only different points from the firstembodiment will be described, and the description of similar points willbe omitted.

As shown in FIG. 5(B), an antibacterial mask 52 according to the secondembodiment includes a filter 102. The filter 102 includes the outerlayer 11 and the inner layer 12. A plurality of second piezoelectricfibers 32 are arranged in the inner layer 12 on the side of the secondprincipal surface 22.

When the filter 102 is stretched in use, positive charges are generatedon the surfaces of the second piezoelectric fibers 32 in the inner layer12. When negatively charged germs and fungi 81 that are discharged fromthe user U come close to the side of the second principal surface 22,the positive charges generated by the second piezoelectric fibers 32attract such germs and fungi 81 to the inner layer 12. This can preventthe germs and fungi 81 discharged from the user U from being inhaledinto or adhering to the user U again by respiratory or the like.Further, since the germs and fungi 81 are once attracted to the filter102, the antibacterial effect can be effectively exerted on the germsand fungi 81 that are collected by the electric charge generated in thefilter 102.

Further, the filter 102 can generate a positive charge only whenstretched. It does not generate a positive charge when not used, forexample, during storage. Therefore, since a positive charge is generatedduring storage, it is possible to prevent unnecessary germs and fungi 81from adhering to the filter 102.

The entire filter 102 may be formed of the second piezoelectric fibers32. The filter 102 may have a filter formed of the second piezoelectricfibers 32 added in a frame shape to the margin of the filter formed ofan ordinary cloth. When the filter formed of the second piezoelectricfibers 32 is provided in a frame shape, the ordinary cloth positioned atthe center thereof is likely to attract the germs and fungi 81. Thus, itis possible to further prevent the germs and fungi 81 from beingabsorbed into a body by attracting the germs and fungi 81 that have notbeen successfully attracted by the second piezoelectric fibers 32 to theordinary cloth.

In the case where the ordinary cloth is combined with the filter 102, apositive charge generated from the entire filter 102 becomes smaller, ascompared with the case where the entire filter 102 is formed of thesecond piezoelectric fibers 32, so that the effect of attracting thegerms and fungi 81 becomes weak. However, since the ordinary cloth isexcellent in hygroscopicity, the combination of the ordinary cloth withthe filter 102 allows air permeability to be ensured.

In the case where the ordinary cloth is combined with the filter 102,the ratio of the ordinary cloth to the second piezoelectric fibers 32 ispreferably 2:8 to 8:2 in terms of an area ratio. When the filter 102includes the ordinary cloth at a given ratio, it can ensure airpermeability. Further, when the filter 102 includes the secondpiezoelectric fibers 32 at a given ratio, an effect of sufficientlyattracting the germs and fungi 81 can also be obtained.

The antibacterial mask 52 may have a shape that covers only a mouth of ahuman. The antibacterial mask 52 attracts the germs and fungi 81 spreadfrom the mouth of the human, thereby preventing the germs and fungi 81from reentering into the mouth. Further, since the filter 102 attractsthe germs and fungi 81 in the surroundings, it prevents the germs andfungi 81 around a nose from entering into the nose. Thus, the use of theantibacterial mask 52 having this shape allows the germs and fungi 81 tobe prevented from entering into the mouth or nose, as well as allowingthe user to easily breathe because the nose is exposed to the outside.

The second piezoelectric fibers 32 used in the filter 102 may includeyarns that generate different quantities of electric charges. In thecase where the germs and fungi 81 adhere to the filter 102, a potentialdifference is produced in the filter 102, and the potential differencethus produced can provide an antibacterial effect. The yarns thatgenerate different quantities of electric charges may be the oneobtained by combining yarns having the different number of times oftwisting, the one obtained by combining yarns having the differentnumber of times of twisting partially in a yarn, or the one obtained bycombining both of them.

An antibacterial mask according to the third embodiment will bedescribed hereinbelow. FIG. 6 is a schematic view showing aconfiguration of an antibacterial mask according to the thirdembodiment. In the description of the antibacterial mask 53 according tothe third embodiment, only different points from the first embodimentwill be described, and the description of similar points will beomitted.

As shown in FIG. 6, an antibacterial mask 53 according to the thirdembodiment includes a filter 103. The filter 103 includes the outerlayer 11 and the inner layer 12. A plurality of first piezoelectricfibers 31 are arranged in the outer layer 11 on the side of the firstprincipal surface 21. A plurality of second piezoelectric fibers 32 arearranged in the inner layer 12 on the side of the second principalsurface 22.

When the filter 103 is stretched in use, positive charges are generatedon the surfaces of the second piezoelectric fibers 32 in the inner layer12. This can prevent the germs and fungi 81 discharged from the user Ufrom being inhaled into or adhering to the user U again by respiratoryor the like. Further, since the germs and fungi 81 are once attracted tothe filter 103, the antibacterial effect can be effectively exerted onthe germs and fungi 81 that are collected by the electric chargegenerated in the filter 103.

At the same time, when the filter 103 is stretched, negative charges aregenerated on the surfaces of the first piezoelectric fibers 31 in theouter layer 11. This can prevent the germs and fungi 81 from enteringinto the filter 103.

The first piezoelectric fiber 31 and the second piezoelectric fiber 32used in the filter 103, as well as the first piezoelectric fibers 31used in the filter 101 or the second piezoelectric fibers 32 used in thefilter 102, may include yarns that generate different quantities ofelectric charges.

Antibacterial masks according to fourth and fifth embodiments will bedescribed hereinbelow. FIG. 7(A) is a schematic view showing aconfiguration of an antibacterial mask according to the fourthembodiment, and FIG. 7(B) is a schematic view showing a configuration ofan antibacterial mask according to the fifth embodiment. In thedescriptions of the antibacterial masks according to the fourth andfifth embodiments, only different points from the third embodiment willbe described, and the description of similar points will be omitted.

As shown in FIG. 7(A), an antibacterial mask 54 according to the fourthembodiment includes a filter 104. The filter 104 includes the outerlayer 11 and the inner layer 12. A plurality of first piezoelectricfibers 31 are arranged in the outer layer 11 on the side of the firstprincipal surface 21. A plurality of first piezoelectric fibers 31 and aplurality of second piezoelectric fibers 32 are arranged in the innerlayer 12 on the side of the second principal surface 22.

When the filter 104 is stretched in use, positive charges are generatedon the surfaces of the second piezoelectric fibers 32 in the inner layer12. This can prevent the germs and fungi 81 discharged from the user Ufrom being inhaled into or adhering to the user U again by respiratoryor the like. At the same time, negative charges are generated on thesurfaces of the first piezoelectric fibers 31 in the inner layer 12.Since both positive and negative charges are generated in the innerlayer 12, a relatively large voltage generates between the firstpiezoelectric fiber 31 and the second piezoelectric fiber 32. Thus, theantibacterial effect can be further effectively exerted on the germs andfungi 81 that are attracted in the inner layer 12.

As shown in FIG. 7(B), an antibacterial mask 55 according to the fifthembodiment includes a filter 105. The filter 105 includes the outerlayer 11 and the inner layer 12. A plurality of first piezoelectricfibers 31 and a plurality of second piezoelectric fibers 32 are arrangedin the outer layer 11 on the side of the first principal surface 21. Theplurality of second piezoelectric fibers 32 are arranged in the innerlayer 12 on the side of the second principal surface 22.

When the filter 105 is stretched in use, negative charges are generatedon the surfaces of the first piezoelectric fibers 31 in the outer layer11. This can prevent the germs and fungi 81 from entering into thefilter 105. At the same time, positive charges are generated on thesurfaces of the second piezoelectric fibers 32 in the outer layer 11.Since both positive and negative charges are generated in the outerlayer 11, a relatively large voltage generates between the firstpiezoelectric fiber 31 and the second piezoelectric fiber 32. Thus, theantibacterial effect can be further effectively exerted on the germs andfungi 81 that are left unrebounded in the outer layer 11. In addition,the antibacterial effect can be further effectively exerted on the germsand fungi 81 that are attracted in the inner layer 12.

An antibacterial mask according to the sixth embodiment will bedescribed hereinbelow. FIG. 8 is a schematic view showing aconfiguration of an antibacterial mask according to a sixth embodiment.In the description of the antibacterial mask according to the sixthembodiment, only different points from the third embodiment will bedescribed, and the description of similar points will be omitted.

As shown in FIG. 8, an antibacterial mask 56 according to the sixthembodiment includes a filter 106. The filter 106 includes the outerlayer 11, the inner layer 12, and an intermediate layer 13. Theintermediate layer 13 is arranged between the outer layer 11 and theinner layer 12. A plurality of first piezoelectric fibers 31 and aplurality of second piezoelectric fibers 32 are arranged in theintermediate layer 13.

When the filter 106 is stretched in use, positive charges are generatedon the surfaces of the second piezoelectric fibers 32 in the inner layer12. In the inner layer 12, the positive charges generated by the secondpiezoelectric fibers 32 attract the germs and fungi 81 to the innerlayer 12. Since both positive and negative charges are generated in theintermediate layer 13, a relatively large voltage generates between thefirst piezoelectric fiber 31 and the second piezoelectric fiber 32.Thus, the antibacterial effect can be further effectively exerted on thegerms and fungi 81 that are attracted to the inner layer 12, or are leftunrebounded in the outer layer 11.

The filters 101 to 106 as described above are applicable to productssuch as various clothes or medical members other than the mask. Forexample, the filters 101 to 106 can be applied to underwear(particularly, socks), towels, insoles for shoes, boots, and the like,the whole of sportswear, headwear, bedclothes (including futon,mattress, sheets, pillow, pillow cover, etc.), toothbrush, floss,filters for water purifier, air conditioner, or air purifier, stuffedtoy, pet-related goods (mat for pets, pet clothing, inner for petclothing), various mat products (for foot, hands, or toilet seats),curtain, kitchenware (sponge or dish towel), seats (seats for cars,electric cars, or airplanes), buffer member and facer for motorcyclehelmets, sofa, bandage, gauze, suture, clothing for doctors andpatients, supporter, sanitary supplies, sporting goods (inner materialsfor wear and gloves, or gloves used for material arts), or packagingmaterials.

Among clothes, in particular, socks (or supporters) are inevitablystretched along joints due to the movement by walking and the like.Therefore, the filters 101 to 106 generate electric charges at a highfrequency. In addition, the socks absorb moisture such as sweat or thelike to become a hotbed for growth of bacteria. The filters 101 to 106are, however, capable of inhibiting the growth of bacteria and thusproduces a remarkable effect as applications for measure against odor.

The filters 101 to 106 can also be used as a measure for inhibitingbacteria on body surfaces of animals except a human being. A clothincluding a piezoelectric body is arranged so as to be opposed to atleast a part of a skin of an animal, and an electric charge generatedwhen an external force is applied to the piezoelectric body may inhibitthe growth of bacteria on the animal body surface that is opposed to thecloth. Thus, it is possible to inhibit the growth of bacteria on thebody surface of the animal and to treat ringworm on the body surface ofthe animal by a simple method which is higher in safety than chemicalsor the like.

WO 2015/159832 A discloses a transducer which senses a displacementapplied to a knitted or woven fabric using a plurality of piezoelectricyarns and conductive yarns. In this case, all the conductive yarns areconnected to a detection circuit and a conductive yarn always pairs witha piezoelectric yarn. In WO 2015/159832 A, when an electric charge isgenerated in the piezoelectric yarn, an electron migrates from theconductive yarn to immediately neutralize the electric charge generatedin the piezoelectric yarn. In WO 2015/159832 A, the detection circuitdetects an electric current generated due to the migration of theelectron and outputs the electric current as a signal. Accordingly, inthis case, the generated potential is immediately canceled, so that nostrong electric field is formed between the piezoelectric yarn and theconductive yarn, and the piezoelectric yarn and the piezoelectric yarn,which in turn no antibacterial effect is exerted.

Description will be made hereinbelow by exemplifying a gauze among theabove-mentioned medical members. FIG. 9(A) is a schematic view showing aconfiguration of an antibacterial gauze according to a seventhembodiment, FIG. 9(B) is a schematic view showing a configuration of anantibacterial gauze according to an eighth embodiment, and FIG. 9(C) isa schematic view showing a configuration of an antibacterial gauzeaccording to a ninth embodiment. FIGS. 9(A) to 9(C) show a mainconfiguration alone. In the descriptions of the antibacterial gauzesaccording to the eighth and ninth embodiments, description relating tothe similar configuration to the seventh embodiment will not beprovided.

As shown in FIG. 9(A), an antibacterial gauze 107 according to theseventh embodiment is, for example, an adhesive plaster or the like tobe applied to a wound W in a skin S. The antibacterial gauze 107, aswell as the filter 101, includes the outer layer 11.

When the antibacterial gauze 107 is stretched in use, negative chargesare generated on the surfaces of the first piezoelectric fibers 31 inthe outer layer 11. This allows the germs and fungi 81 to be reboundedin the outer layer 11. An animal cell of the skin S is negativelycharged. The negative charges generated when the first piezoelectricfibers 31 in the outer layer 11 are stretched and the negative chargethat the animal cell of the skin S carries repel one another. Therefore,the animal cell of the skin S is less likely to be attached to theantibacterial gauze 107. The antibacterial gauze 107 is less likely totouch the wound W in the skin S to improve air permeability, so thatwound healing can be hastened. In addition, the electric chargesgenerated by the first piezoelectric fibers 31 stimulate the cell, whichcan thereby further hasten wound healing.

As shown in FIG. 9(B), an antibacterial gauze 108 according to theeighth embodiment has the intermediate layer 13 further laminated on theantibacterial gauze 107 on the outside. The intermediate layer 13includes the first piezoelectric fibers 31 and the second piezoelectricfibers 32.

Since both positive and negative charges are generated in theintermediate layer 13, a relatively large voltage generates between thefirst piezoelectric fiber 31 and the second piezoelectric fiber 32.Thus, the antibacterial effect can be effectively exerted on the germsand fungi 81 that are left unrebounded in the outer layer 11 because ofblood or body fluids adhering to the antibacterial gauze 108. This canrebound the germs and the fungi 81, and can also inhibit the growth ofbacteria.

As shown in FIG. 9(C), an antibacterial gauze 109 according to the ninthembodiment, as well as the filter 106, includes the outer layer 11, theinner layer 12, and the intermediate layer 13. The inner layer 12includes the second piezoelectric fibers 32.

When the antibacterial gauze 109 is stretched in use, positive chargesare generated on the surfaces of the second piezoelectric fibers 32 inthe inner layer 12. The positive charges generated by the secondpiezoelectric fibers 32 in the inner layer 12 and the negative chargethat the animal cell of the skin S carries attract one another.Therefore, the animal cell of the skin S comes in close contact with theantibacterial gauze 109. This relatively blocks air permeability, sothat the affected area which is not desirable to dry can be remedied. Inaddition, the electric charges generated by the second piezoelectricfibers 32 stimulate the cell, which can thereby further hasten woundhealing.

The filters 101 to 106 according to this embodiment have the followingapplications, in addition to the bacteria countermeasure application.

(1) Biologically Acting Piezoelectric Fiber Products

Many tissues constituting a living body have piezoelectric properties.For example, collagen that constitutes a human body is a kind ofprotein, and is contained in a blood vessel, dermis, a ligament, tendon,bones, or cartilage in a large amount. Collagen is a piezoelectric body,and a collagen-oriented tissue may exhibit extremely large piezoelectricproperties. Many reports about piezoelectric properties of bones havealready been made (see, for example, “Seitai Kobunshino Atsudenki(Piezoelectricity of biopolymers)”, Polymer vol. 16 (1967) No. 9, p.795-800 written by Eiichi FUKADA). Therefore, a filter including thefirst piezoelectric fibers 31 or the second piezoelectric fibers 32produces an electric field, and when the electric field alternates orthe strength of the electric field varies, the piezoelectric body of theliving body vibrates by inverse piezoelectric effect. A minute vibrationis applied to a portion of the living body, for example, capillary ordermis, due to the alternating electric field produced by the firstpiezoelectric fibers 31 and/or the second piezoelectric fibers 32, ordue to the variation in the strength of the electric field, so that theimprovement of blood flow in the portion can be encouraged. This mayaccelerate the healing of a skin disorder or wound. Therefore, thefilters 101 to 106 serve as biologically acting piezoelectric fiberproducts.

(2) Piezoelectric Fiber Products For Attracting Substance

As described above, the first piezoelectric fibers 31 generate negativecharges when an external force is applied thereto. The secondpiezoelectric fibers 32 generate positive charges when an external forceis applied thereto. Therefore, the first piezoelectric fibers 31 attracta substance having a positive charge (e.g., particles such as pollen)and the second piezoelectric fibers 32 attract a substance having anegative charge (e.g., harmful substances such as yellow dust).Accordingly, in the case where the filters 103 to 106 including thefirst piezoelectric fiber 31 and the second piezoelectric fiber 32 areapplied to, for example, medical articles such as a mask, or filters forair-conditioning devices such as an air conditioner or an air purifier,they can attract fine particles such as pollen and yellow dust.Description will be made hereinbelow by way of examples.

FIG. 10(A) is a schematic view of a filter according to a tenthembodiment. FIGS. 10(B) and 10(C) are cut end views taken along the lineC-C in FIG. 10(A). FIGS. 11(A) to 11(D) are schematic views showingconfigurations of the filter according to the tenth embodiment, and areviews for describing the variations in the filter. In the description ofthe filter according to the tenth embodiment, description relating tothe similar configuration to the above-mentioned embodiments will not beprovided. FIGS. 10(A) to 10(C) show only a frame member 111 thatconstitutes a filter, the first piezoelectric fibers 31, and the secondpiezoelectric fibers 32, and the configuration that constitutes theother filter of ordinary yarns or the like is omitted. The frame member111 is an example of the “holding member” in the present invention.

A filter 110 according to the tenth embodiment is used as a filter foran air conditioner or an air purifier, for example. As shown in FIG.10(A), the filter 110 includes the frame member 111 and a filter portion112. The filter portion 112 is fixed to the frame member 111.

The filter portion 112 is a woven fabric or a nonwoven fabric includingthe first piezoelectric fibers 31 or the second piezoelectric fibers 32.For example, a portion of the warps that constitute the filter portion112 is the first piezoelectric fibers 31 and a portion of the wefts thatconstitute the filter portion 112 is the second piezoelectric fibers 32.Here, for convenience of description, a filter constituted so as toprincipally generate a positive charge during nonuse and so as toprincipally generate a negative charge when extended will be describedas the filter portion 112. In the filter portion 112, only the quantityof either positive charge or negative charge may vary.

As shown in FIG. 10(B), the filter portion 112 maintains a flat shapeduring nonuse. During nonuse, the filter portion 112 may be fixed to afixing member such as the frame member 111 while a tension is applied inthe weft direction. That is, the filter portion 112 is fixed to a fixingmember such as the frame member 111 while the second piezoelectricfibers 32 are in an extended state. In this case, for example, as shownin FIG. 11(A), the filter portion 112 in use is easily applied withtension and can generate a positive charge.

When the filter portion 112 in use is exposed to wind in the directionindicated by the arrow, it vibrates while being deformed as shown inFIG. 10(C). The vibration of the filter portion 112 refers to repetitionof the state shown in FIG. 10(C) and the state shown in FIG. 10(B).

When the filter portion 112 vibrates, the first piezoelectric fibers 31and the second piezoelectric fibers 32 of the filter portion 112 arestretched. At this time, in particular, the first piezoelectric fibers31 of the warps are largely stretched, so that a negative charge islikely to be generated. Therefore, when the filter portion 112 isdeformed, a negative charge is generated in the filter portion 112 asshown in FIG. 11(B), for example. This weakens an attraction forcebetween dust 82 once attracted on the surface side and the filterportion 112. Accordingly, the dust 82 attracted to the filter portion112 easily moves in the filter portion 112. The filter portion 112 inuse vibrates while being continuously deformed, so that the condition ofgenerating electric charge continues to vary.

Here, in the case where there is a positive charge on the inner side ofthe filter portion 112, the dust 82 is pulled to the inner side as shownin FIG. 11(C). Thus, the filter portion 112 holds the dust 82 inside andvibrates, to thereby allowing the filter portion 112 to further generatea positive charge on its surface. Therefore, as shown in FIG. 11(D), thefilter portion 112 can further attract the dust 82 on its surface. Thus,the filter portion 112 can exert an attraction force longer byvibration.

The filter portion 112 preferably has a structure in which the meshbecomes coarser toward the surface of the filter portion 112, and themesh becomes finer toward the inside thereof. The filter 110 attractsthe dust 82 on the surface of the filter portion 112. Thereafter, thedust 82 attracted to the surface moves as the filter portion 112 movesor as the condition of generating electric charge varies. At this time,when the surface of the filter portion 112 is coarse, the dust 82 islikely to enter into the filter portion 112. Therefore, the filterportion 112 is likely to absorb the dust 82 once captured on the surfaceof the filter portion 112 into the filter portion 112. Conversely, thefilter portion 112 allows the dust 82 once absorbed into the filterportion 112 to be hardly flown outside the filter portion 112. Thus, thefilter portion 112 can enhance the effect of holding the dust 82.

In FIGS. 10(A) to 10(C), the first piezoelectric fibers 31 of the weftsgenerate negative charges during extension, and the second piezoelectricfibers 32 of the warps generate positive charges during extension.However, the second piezoelectric fibers 32 may be used as wefts and thefirst piezoelectric fibers 31 may be used as warps. For example, in thecase of using the first piezoelectric fibers 31 as both warps and wefts,negative charges are generated during extension, and in the case ofusing the second piezoelectric fibers 32 as both warps and wefts,positive charges are generated during extension.

Next, modifications 1 to 3 of the filter 110 according to the tenthembodiment will be described hereinbelow. FIG. 12(A) is a schematic viewof a modification 1 of the filter according to the tenth embodiment, andFIGS. 12(B) and 12(C) are cut end views taken along the line D-D in FIG.12(A). FIG. 13(A) is a schematic view of a modification 2 of the filteraccording to the tenth embodiment, and FIGS. 13(B) and 13(C) are cut endviews taken along the line E-E in FIG. 13(A). FIG. 14(A) is a schematicview of a modification 3 of the filter according to the tenthembodiment, and FIGS. 14(B) and 14(C) are cut end views taken along theline F-F in FIG. 14(A). In modifications 1 to 3, only different pointsfrom the filter 110 according to the tenth embodiment will be described,and the other description will be omitted.

As shown in FIGS. 12(A) and 12(B), a filter 120 according tomodification 1 includes a frame member 121 having a different shape fromthe frame member 111. The frame member 121 is formed in a lattice shape.A filter portion 122 is fixed to the frame member 121. Therefore, thefirst piezoelectric fibers 31 and the second piezoelectric fibers 32 arefixed to the frame member 121 while being divided into small sections.The frame member 121 is an example of the “holding member” in thepresent invention.

As shown in FIG. 12(C), when the filter 122 in use is exposed to wind inthe direction indicated by the arrow, it vibrates while being deformed.In the case where the frame member 121 is formed of a material that isless likely to be stretched as compared with the filter portion 122, thefilter portion 122 vibrates in each section divided by the frame member121. Thus, the filter portion 122 is entirely uniformly stretched ascompared with the filter portion 112.

In the case of forming the frame member 121 into a lattice shape havinguniform sections, the filter portion 122 in each lattice section is moreuniformly stretched. Therefore, electric charge uniformly generates inthe entire filter portion 122. This allows the filter 120 to uniformlyabsorb the dust 82 at the filter portion 122. Therefore, the filter 120can prevent a part of the filter portion 122 from clogging. It ispossible to properly provide the filter 120 with a strength suitable foruse condition by changing the material or size of the frame member 121.

As shown in FIG. 13(A), a filter 130 according to modification 2includes a frame member 131 having a lattice shape as in modification 1and a filter portion 132 having a different shape. As shown in FIGS.13(A) and 13(B), the filter portion 132 is three-dimensionally formed soas to protrude from one principal surface 133 of the filter 130 towardthe other principal surface 134 thereof. Since the surface area of thefilter portion 132 is three-dimensionally formed, it is large ascompared with the filter portion 122 in modification 1. The frame member131 is an example of the “holding member” in the present invention.

As shown in FIG. 13(C), when the filter 132 is exposed to wind in thedirection indicated by the arrow, it vibrates while being deformed. Atthis time, since the surface area of the filter portion 132 is large,the filter 130 can attract and hold more dust 82 than the filter 120.

As shown in FIG. 14(A), a filter 140 according to modification 3includes a filter portion 142 having a different shape from the filter110. The filter portion 142 is formed in a bellows shape as shown inFIGS. 14(A) and 14(B). Therefore, since the surface area of the filterportion 140 is largely formed, the filter 140 can attract and hold moredust 82.

As shown in FIG. 14(C), when the filter 142 in use is exposed to wind inthe direction indicated by the arrow, it vibrates while being deformed.At this time, since the filter portion 142 is formed in a bellows shape,the movement becomes large as compared with the case of forming thefilter in a flat shape like the filter 110. Thus, the filter 140 cangenerate larger electric charge than the filter 110. That is, the filter140 has a higher force of attracting the dust 82 as compared with thefilter 110. Accordingly, the filter 140 attracts and holds the dust 82more quickly than the filter 110.

Further, since the filter portion 142 is formed in a bellows shape,vibration occurs also in a direction different from the directionindicated by the arrow as shown in FIG. 14(C). For example, the filterportion 142 generates vibration in a direction perpendicular to thearrow shown in FIG. 14(C) by spirally moving air at a portion 145recessed from the wind receiving side in the filter portion 142. Thus,the filter portion 142 performs a more complicated movement, so that theoccurrence of electric charge in the filter portion 142 becomes morecomplicated. Therefore, the filter 140 is more likely to absorb the dust82 that has been once captured on the surface of the filter portion 142,into the filter portion 142.

FIG. 15 is a schematic view showing a case where a filter is used in anair-conditioning device. In FIG. 15, a case of using the filter 110 willbe described as an example. An air-conditioning device 150 includes aninlet port 151, an exhaust port 152, and a communicating passage 153that communicates between the inlet port 151 and the exhaust port 152.The filter 110 is arranged in the communicating passage 153, forexample. Accordingly, it is possible to attract fine particles such aspollen or yellow dust in the air that circulates in the communicatingpassage 153.

A configuration in which an electrical conductor is used in a core yarn,an insulator is wound around the electrical conductor, and an electriccurrent is flown into the electrical conductor to generate an electriccharge is also a fiber that generates an electric charge. It should benoted that a piezoelectric body produces an electric field by apiezoelectric effect, so that no power supply is required, and anelectric shock may not occur. The life of the piezoelectric body lastslonger than the antibacterial effect of chemicals or the like. Further,the piezoelectric body may cause an allergic reaction less thanchemicals. In recent years, exhibition of resistant bacteria due tochemicals, particularly, antibiotics has been a major problem. However,the sterilization method according to the present invention is notconsidered to generate resistant bacteria in terms of its mechanism.

As the fiber that generates a negative electric charge on its surface, aZ yarn using PDLA, as well as an S yarn using PLLA, is considered. Inaddition, as the fiber that generates a positive electric charge on itssurface, an S yarn using PDLA, as well as a Z yarn using PLLA, isconsidered.

The S yarn using PLLA as the fiber that generates a negative electriccharge on its surface in stretching, and the Z yarn using PLLA as thefiber that generates a positive electric charge on its surface duringstretching are exemplified, but they are not limited to theseconfiguration. For example, instead of the first piezoelectric fiber 31,other fibers can be used as long as it generates a negative electriccharge on its surface during stretching. Similarly, instead of thesecond piezoelectric fiber 32, other fibers can be used as long as itgenerates a positive electric charge on its surface during stretching.Conversely, a fiber that generates a positive or negative electriccharge during shrinking can also be used.

Further, in the present embodiment, as long as a potential difference isproduced between the first piezoelectric fibers 31 and the secondpiezoelectric fibers 32, an effect is obtained. Even if an electriccharge of the same polarity generates in the first piezoelectric fiber31 and the second piezoelectric fiber 32, a similar effect can beobtained as long as the amount of the electric charge generated in eachof the piezoelectric fibers is different. For example, a combination ofpiezoelectric fibers having the different number of twists, acombination of piezoelectric fibers having the different number offilaments, a combination of piezoelectric fibers having differentfilament diameters, a combination of piezoelectric fibers havingdifferent piezoelectric constants, and a combination of piezoelectricfibers having these conditions combined are included.

The filter according to the present embodiment can be adopted to, forexample, a screen door and the like, in addition to the above-mentionedembodiments. In the screen door, a mesh sheet including the filter isfixed to a frame in a tension applied state. In a normal state, thefilter is maintained under tension. Accordingly, a tension is applied tothe filter by a minute vibration generated by an external environment,so that an antibacterial effect or the like can be easily exerted.

Finally, the present embodiments should therefore be considered in allrespects as illustrative and not restrictive. The scope of the inventionis given by the appended claims, rather than the preceding embodiments.Further, all variations and equivalents which fall within the range ofthe claims are intended to be embraced therein.

DESCRIPTION OF REFERENCE SYMBOLS

21: First principal surface

22: Second principal surface

31: First piezoelectric fiber (right-twisted yarn: S yarn)

32: Second piezoelectric fiber (left-twisted yarn: Z yarn)

51, 52, 53, 54, 55, 56: Antibacterial mask

101, 102, 103, 104, 105, 106, 110, 120, 130, 140: Filter

107, 108, 109: Antibacterial gauze (filter)

The invention claimed is:
 1. A filter comprising: a plurality of fibersarranged to form a first principal surface and a second principalsurface opposite the first principal surface; of the plurality offibers, a plurality of first piezoelectric fibers that generate negativecharges by stretching are arranged at least on a side of the firstprincipal surface; and a holding member, and wherein the plurality offirst piezoelectric fibers are fixed to the holding member in atensioned state.
 2. The filter according to claim 1, wherein the filteris a fabric having warps and wefts made of the plurality of firstpiezoelectric fibers, and the warps and the wefts are fixed to theholding member.
 3. The filter according to claim 1, wherein, of theplurality of fibers, a plurality of second piezoelectric fibers thatgenerate positive charges by stretching are arranged at least on a sideof the second principal surface.
 4. The filter according to claim 1,wherein, of the plurality of fibers, a plurality of second piezoelectricfibers that generate positive charges by stretching are arranged atleast on a side of the second principal surface, and a plurality ofthird piezoelectric fibers that generate negative charges by stretchingare arranged at least on a side of the second principal surface.
 5. Thefilter according to claim 1, wherein, of the plurality of fibers, aplurality of second piezoelectric fibers that generate positive chargesby stretching are arranged at least on a side of the first principalsurface, and a plurality of third piezoelectric fibers that generatepositive charges by stretching are arranged at least on a side of thesecond principal surface.
 6. The filter according to claim 1, furthercomprising an intermediate layer between the first principal surface andthe second principal surface, wherein, of the plurality of fibers, aplurality of second piezoelectric fibers that generate positive chargesby stretching are arranged at least on a side of the second principalsurface, and a plurality of third piezoelectric fibers that generatepositive charges by stretching and a plurality of fourth piezoelectricfibers that generate negative charges by stretching are arranged in theintermediate layer.
 7. The filter according to claim 1, wherein theplurality of fibers include a cloth that does not include piezoelectricfibers, and a ratio of the cloth to the plurality of first piezoelectricfibers is 2:8 to 8:2.
 8. An air-conditioning device comprising: an inletport; an exhaust port; a communicating passage between the inlet portand the exhaust port; and a filter according to claim 1 arranged in thecommunicating passage, the filter comprising: a plurality of fibersarranged to form a first principal surface and a second principalsurface opposite the first principal surface; and of the plurality offibers, a plurality of first piezoelectric fibers that generate negativecharges by stretching are arranged at least on a side of the firstprincipal surface.
 9. A filter comprising: a plurality of fibersarranged to form a first principal surface and a second principalsurface opposite the first principal surface; of the plurality offibers, a plurality of first piezoelectric fibers that generate positivecharges by stretching are arranged at least on a side of the secondprincipal surface; and a holding member, and wherein the firstpiezoelectric fibers are fixed to the holding member in a tensionedstate.
 10. The filter according to claim 9, wherein the filter is afabric having warps and wefts made of the plurality of firstpiezoelectric fibers, and the warps and the wefts are fixed to theholding member.
 11. The filter according to claim 9, wherein, of theplurality of fibers, a plurality of second piezoelectric fibers thatgenerate negative charges by stretching are arranged at least on a sideof the second principal surface.
 12. The filter according to claim 9,wherein the plurality of fibers include a cloth that does not includepiezoelectric fibers, and a ratio of the cloth to the plurality of firstpiezoelectric fibers is 2:8 to 8:2.
 13. An air-conditioning devicecomprising: an inlet port; an exhaust port; a communicating passagebetween the inlet port and the exhaust port; and a filter arranged inthe communicating passage, the filter comprising: a plurality of fibersarranged to form a first principal surface and a second principalsurface opposite the first principal surface; and of the plurality offibers, a plurality of first piezoelectric fibers that generate positivecharges by stretching are arranged at least on a side of the secondprincipal surface.